This invention relates to charged particle spectroscopy and particularly, although not exclusively, to an improved instrument and components for use in electron spectroscopy, specifically Auger electron spectroscopy.
Instrumentation for use in electron spectroscopy makes use of electrons which are emitted from a substance after being bombarded or irradiated with electrons from a source such as an electron gun. The technique to which the invention is specifically directed is to one known as Auger electron spectroscopy. In this type of a technique, a target sample material is placed in a vacuum, usually below about 10.sup.-7 Torr, and upon being bombarded with electrons from some source, such as an electron gun, the sample gives off a variety of emissions. Among these are X-rays, secondary electrons, and reflected primary electrons from the source. The sample gives off Auger electrons (a particular class of secondary electrons) in the manner which is well known in the literature.
In the art of Auger electron spectroscopy, instruments making use of cylindrical mirror analyzers are known which analyze the energy and the energy spectrum of Auger electrons emitted by the sample material by injecting the electrons into a radial electric field produced between a pair of coaxially mounted electrodes held at different electric potentials. Auger electrons injected into the radial electric field between the cylindrical electrodes are deflected by the field toward the common axis of the electrodes. Electrons of a predetermined energy are thereby brought to a focus. By positioning a collector apparatus at this focus, electrons of a predetermined energy are selected and detected. By sweeping the voltage impressed across the cylindrical electrodes through a range of values, and detecting as a function of these applied potentials such electrons as are collected, the energy spectrum of the injected electrons may be plotted and determined.
Prior art instruments incorporate a collector which collects only those electrons which pass close to the analyzer axis. Consequently, any magnetic field or the like which deflects the paths of such electrons reduces the likelihood of their collection. This has prevented the use of coaxial magnetic lenses and the like in these instruments in the past since such lenses affect the electron's path.